Titanium chelate modified nylon magnet wire insulation coating

ABSTRACT

A magnet wire enamel having improved runnability and insulating properties is described comprising nylon containing 0.25% to 20% by weight titanium chelate. The nylon can be a sole coat, outermost coating, or bond coat.

This is a division of application Ser. No. 660,197 filed on Oct. 12,1984.

TECHNICAL FIELD

The field of art to which this invention pertains is polyamide coatingcompositions, and particularly nylon coating compositions on insulatedmagnet wire substrates.

BACKGROUND ART

Because of their relative low cost and the desirable handling propertiesthey provide to polymer insulated magnet wire, nylon topcoats have beenused in the magnet wire area for several years. However, such coatingsare not without problems. For example, on high temperature wire such asmagnet wire coated with polyester base coats, nylon overcoats havesuffered from such things as ring cracks (circular cracks perpendicularto the major axis of the coated wire) particularly in dry weather andsuch cracks can cause catastrophic wire failure. Furthermore, because ofthe relatively low solidification point of nylon, temperature changescan cause great difficulty in providing a smooth coating on wire. Partof this problem results from the fact that when applying plural coatingsof the nylon, successive coats redissolve previously applied coats, thusproducing smoothness problems.

Accordingly, what is needed in this art is a nylon composition whichovercomes such problems.

DISCLOSURE OF INVENTION

The present invention is directed to an improved magnet wire enamelcomposition comprising nylon modified by reaction with a titaniumchelate. The titanium chelate reacts with the amine and carboxyl groupson the nylon molecule resulting in a nylon modified dimer with bothimproved application to magnet wire substrates and improved wireproperties after application to the magnet wire substrates. The titaniumchelates are typically reacted into the nylon in an amount of about0.25% to about 10% by weight of the nylon present in the enamelcomposition.

Another aspect of the invention is electrically insulated magnet wirecontaining a plurality of polymer layers of insulation where at leastone of the layers comprises the above-described nylon enamel.

Another aspect of the invention comprises a method of forming polymerinsulated magnet wire having a plurality of polymeric insulating layerswhere at least one of the layers is the nylon material described above.

These and other advantages of the present invention will become moreapparent from the following description.

BEST MODE FOR CARRYING OUT THE INVENTION

Any nylon material can be catalyzed with the titanate described herein.Typically nylon 6; nylon 11; nylon 6,6; nylon 6,12; etc. are used. Thetitanium chelates used are organic chelates, specifically alkylchelates, and preferably titanium acetyl acetonate, titanium ethylacetyl acetonate, titanium triethanolamine chelate, and the ammoniumsalt of titanium lactic acid chelate. Typically the nylon layer is usedas an overcoat on such things as standard polyester (such as THEICpolyester), polyurethane or polyvinyl formal resins. However, it canalso be used in conventional constructions as an intermediate layer(bond coat) between multiple layers of, e.g. polyurethane or as a solecoat.

Although not wishing to be bound by any particular theory it is believedthat the titanium chelate nylon reaction occurs as follows: ##STR1##represents the nylon moiety. This new molecule ##STR2## (where R is analkyl group stemming from the chelate) is very stable because bondingtwo carboxyl ##STR3## groups to a titanium center uses up all thecoordination sites on the titanium. ##STR4## This molecule, which wewill refer to as a nylon dimer, has a chemistry of its own when appliedto the wire substrate. For example, when applied to a previously appliedbase coat such as an hydroxyl rich polyester as discussed above, thefollowing reactions take place: ##STR5## The base coat surface ishydroxyl rich and can react with one or two of the remaining alkoxygroups on the titanium nylon dimer. The above equation is writen for thereaction of two alkoxy groups.

In a sole nylon coat or in the body of the film which does not interactwith other layers the following reaction takes place: ##STR6## where theO on the Ti reacts with available ##STR7##

While the polymers according to the present invention can be used on anyelectrical conductor they are preferably used on wires and specificallyon magnet wires. The wires are generally copper or aluminum and rangeanywhere from 4 AWG to 42 AWG (American Wire Gauge) in diameter, with 18AWG being the most commonly coated wire. Wire coatings can be anywherefrom 0.1 to 5 mils or any thickness desired and preferably about 3.2mils on 18 AWG wire. As stated above the coatings can be used as part ofa multicoat system in combination with conventional polymer insulationsuch as polyesters, polyurethanes, polyvinyl formal, polyimides,polyamideimides, etc. and combinations thereof. The polymer coatings canalso contain lubricants either externally on the nylon or admixed withthe nylon.

Typical multicoat systems include such things as THEIC polyester basecoats with nylon topcoats with the nylon comprising about 20% to about25% of the total thickness. When used as a bond coat, i.e. anintermediate layer between two additional layers of polymer insulation(such as a polyurethane base coat, the nylon bond coat, and a polyvinylbutyral topcoat, i.e. a solderable composition) and nylon typicallyrepresents about 5% to about 10% of the total wire product.

The enamels according to the present invention can be applied by anyconventional means such as coating dyes, roller or felt application withviscosity adjustments made accordingly. Viscosity adjustments can bemade by dilution with appropriate enamel solvents or diluents. Suchsolvents are typically cresylic acids, and methyl pyrrolidone,N,N-dimethyl or N,N-diethyl formamide and N,N-diethyl acetamide, alongwith any conventional hydrocarbon diluents such as xylene, Solvesso™ 100(Exxon) or D59™ hydrocarbon (Drake Petroleum Company).

Conventional ovens can be used to heat treat the magnet wire afterapplication of the nylon. Typical inlet oven temperatures are of theorder of 500° F. to 700° F., preferably about 580° F. and outlet oventemperatures of about 800° F. to 1100° F., and preferably about 900° F.are used for drying and curing.

In order to demonstrate the improved and unexpected properties of nylonmodified with the titanium chelates according to the present invention,a series of experiments were run to ascertain the effects of variouschelates on the enamel.

The following table shows the properties of wire made from reprocessedscrap nylon repelletized.

These enamels were tested on 18 AWG copper with THEIC polyester basecoat in a Df (250° C.) as low as 0.03.

                  TABLE                                                           ______________________________________                                                       %        Mandrel  DF @  Heat                                   Additive       Additive Pull     250° C.                                                                      Shock                                  ______________________________________                                        Titanium Ethylaceto-                                                                         1.6      Pass     .65   OK                                     acetonate (Tyzon ® DC,                                                    DuPont Co.)                                                                   Titanium Triethanolamine                                                                     1.5      Pass     .05                                          Chelate Solution                                                              (Tyzor TE)                                                                    Titanium Lactic Acid                                                                         1.5      Pass     .62   OK                                     Chelate Ammonium Salt                                                         (Tyzor LA)                                                                    Titanium Acetylacetonate                                                                      .4      Pass     .03   OK                                     Solution (Tyzor AA)                                                           Titanium Acetylacetonate                                                                     1.0      Pass     .03   OK                                     Solution                                                                      Control (No Titanate)                                                                        0.0      Fail     .05   OK                                     ______________________________________                                    

The Tg and melt point of modified and unmodified nylons are compared andfound not to have been changed by the dimerization. This absence ofchange was to be expected. Chelate treated nylon still passes the HClacid blush test.

EXAMPLE

One part per hundred by weight of titanium acetyl acetonate was reactedwith nylon made from reprocessed scrap nylon 6,6 fibers repellitized. A15% by weight mixture of this modified nylon was made up with cresol,phenol, and/or xylene by mixing for one-half hour to form a homogeneoussolution. This mixture was coated on 18 AWG wire as described above. Thechange in properties were as shown in the table below:

    ______________________________________                                                  Df (250° C.)                                                                    Mandrel pull                                                                              Snap/Flex                                      ______________________________________                                        Enamel Without                                                                            .03         1          Pass                                       Chelate     .07         1          Pass                                                   .12        14          Pass                                       Same Enamel With                                                                          .04         10+        Pass                                       1% Titanium Acetyl                                                                        .06        10          Pass                                       Acetonate   .11         10+        Pass                                       ______________________________________                                    

In this table Df (Dissipation Factor) values of between about 0.12 andabout 0.28 represent a cured enamel with values less than about 0.11representing overcure. In the mandrel pull column, values greater thanabout 10 represents a "pass".

As stated above besides providing improved sole coats and topcoats forvarious polymer constructions, the modified nylon according to thepresent invention also produces an improved intermediate layer (bondcoat) in multiple layer constructions.

Although this invention has been shown and described with respect todetailed embodiments thereof, it will be understood by those skilled inthe art that various changes in form and detail thereof may be madewithout departing from the spirit and scope of the claimed invention.

I claim:
 1. A method of coating a magnet wire substrate comprisingapplying to an electrically conductive wire substrate at least one layerof an enamel composition comprising nylon reacted with 0.25% to 20% byweight of a titanium chelate.
 2. The method of claim 1 wherein thetitanium chelate is selected from the group consisting of titaniumacetyl acetonate, titanium ethyl acetyl acetonate, titaniumtriethanolamine chelate, and the ammonium salt of titanium lactic acidchelate.
 3. The method of claim 1 which includes applying a layer ofpolyester to the electrically conductive substrate prior to applicationof the nylon.
 4. The method of claim 1 including applying a layer ofpolyurethane on the electrically conductive substrate prior to applyingthe nylon layer and applying a layer of polyvinyl butyral over the nylonlayer.